Deep suburban antipathy toward President Donald Trump has turned the old GOP electoral coalition inside-out in many areas in 2017 and 2018 — like Ohio’s 12th District, where the president backed Troy Balderson in Tuesday's special election. | Scott Olson/Getty Images

The vote breakdown in Ohio’s special election this week amplified a trend that's been building in the suburbs during the Trump era — and illustrated how the traditional Republican path to victory has been upended in key congressional districts.

Deep suburban antipathy toward President Donald Trump has turned the old GOP electoral coalition inside-out in many areas in 2017 and 2018 — like Ohio’s 12th District, which for two decades sent former Rep. Pat Tiberi to Congress on the back of his popularity in the Columbus suburbs. His anointed successor, Republican Troy Balderson, took a different path to a small special-election lead, instead building on Trump’s rural strength while Democrat Danny O'Connor cut deeply into Tiberi’s old base.

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In Columbus’ Franklin County, where Tiberi regularly received more than 55 percent support, O’Connor held Balderson to just one-third of the special election vote. In Delaware County — a wealthier, whiter bedroom community to the north — Balderson scraped together a majority where Tiberi used to win 70-plus percent. But the further Balderson got from the city, the better he performed compared to Tiberi’s baselines, taking up to 71 percent of the vote in further-flung counties.

It’s a shift that was underway before Trump arrived on the political scene — but the president accelerated it. In 2016, Tiberi and some other Republicans even combined their traditional suburban power with growing rural strength on Trump’s ticket. But that combination has proven unattainable in elections during the president’s tumultuous first term, and Republicans across the country will have to confront the full force of that change in the November elections.

Many House Republicans hope to hold back the tide by virtue of long records and personal appeal in their districts, along with key support in rural stretches. But many of them will also be running in suburbs that already tilt more heavily Democratic than the double-digit Trump districts, including Ohio’s 12th, that hosted special elections in 2017 and 2018. There are 68 GOP-held House seats that lean more Democratic than the Ohio seat, according to the Cook Political Report.

“While a great GOP win, Delaware County is the suburban abyss a lot of Republican candidates across the country are looking into as general elections begin,” said Nick Everhart, a Republican consultant.

The emerging House battleground map includes a number of districts dominated by younger, highly educated, more diverse suburbs like the Franklin County core of the Tiberi district. Open seats in Orange County, California, and the Philadelphia suburbs, and GOP Rep. Barbara Comstock’s Northern Virginia seat bordering Washington, D.C., have tilted toward Democrats this year behind that potent demographic mix.

Evidence out of Ohio as well as national polls show those voters are also more excited to vote in 2018. About 42 percent of Franklin and Delaware County turned out in the special election, compared to the rural counties, where turnout hovered between 27 and 32 percent.

Yet more tossup House districts that will be at the center of the fight for the House feature a similar geographic mashup to Ohio’s 12th District — a mix of suburban, exurban and rural voters in districts that sprawl away from cities like Charlotte, Chicago and Cincinnati.

“In districts with suburban and rural geographies, we have two challenges: You’ve got to run up turnout in the rural areas, and you’ve got to focus on persuasion in the suburban areas,” said Robert Blizzard, a Republican pollster who worked on Balderson’s campaign. “From a campaign standpoint, that’s a tough needle to thread. It takes both time and money.”

Running with an unpopular president in office, many Republicans have fared even worse in big suburban counties in 2017 and 2018 than Trump did in 2016. But they have not bled as much support in outer suburbs like Delaware County, where Balderson held on to win in Ohio.

“Since the advent of Trump, the suburbs are moving more dramatically to the Democrats, and as you move out away from the city center farther out, then it changes according to education and income,” said John Weaver, a Republican strategist who works with Ohio Gov. John Kasich.

This political drift exacerbates the bifurcation of urban and rural communities, a tension that the Democratic Congressional Campaign Committee exploited in the final hours of the campaign, after Balderson told supporters Monday night that they “don’t want somebody from Franklin County representing us.” That was seen as a put-down of the largest, and most citylike, part of the district. The DCCC sent 60,000 Election Day texts about Balderson’s remark, according to a source familiar with the committee’s investments.

Delaware County is “still a few years behind Franklin County,” but it’s “trending in the same direction,” said Tom Bonier, a Democratic strategist who leads the data and analytics firm TargetSmart.

“O’Connor underperformed [in Delaware County], and Balderson overperformed; that’s where you see Kasich’s impact,” Bonier continued, referring to Balderson’s endorsement from Kasich, who has long cultivated suburban voters in Delaware County dating back to his decades representing them in Congress.

But surrogates like Kasich can’t be everywhere in the November elections — nor can the outside groups that spent $3.5 million on TV ads alone backing Balderson, according to Advertising Analytics.

At the same time, Republican strength in rural areas under Trump poses an issue for Democrats across the House map. Trump’s last-minute stump appearance in the House special election in Pennsylvania last March juiced turnout “by 3 or 4 points,” said John Brabender, a GOP consultant who worked on Republican Rick Saccone’s bid. It wasn’t enough for Saccone, who lost to Rep. Conor Lamb (D-Pa.), but Brabender said the president’s visit to Ohio last weekend probably “did the same for the Ohio race, like it did for us.”

“There are a lot of people out there who are supportive of the president’s agenda, and they’re much more loyal to this president than they are to the Republican Party,” Brabender said. “The challenge for Republicans between now and November is to harvest the president’s ability to go find voters who have not always a strong affiliation for one party or the other, but do for this president and get them to show up and vote Republican.”

Just as the GOP hopes individual incumbents can withstand pressure in the suburbs, Democrats believe that candidates running in rural and exurban districts — many of whom are running for office for the first time — will be able to win back some of their party’s former voters who have flocked to the GOP in recent years.

“Danny O’Connor was a strong, but fairly generic candidate,” said one Democratic strategist working on House races. “There are a lot of better districts and a lot of better candidates out there.”

The shift away from Democrats in rural areas fueled the party’s decline during the years of President Barack Obama’s administration. But now, Democrats hope that the reverse trend in the suburbs will drive a resurgence — and that 21 months of off-year and special elections foreshadow the November midterms.

“A Republican in Delaware County would normally get about 70 percent of the vote, and this was 50-50,” Kasich said in an interview with MSNBC on Wednesday. “In areas, suburbs particularly, where Republicans would win, the Republican lost.”